For a given bond, I would like to perform an NBO calculation for each structure while scanning the bond lengths.

  1. Can I use Opt=ModRedundant in combination with pop=nbo? Simply specifying both keywords would only perform the NBO calculation for the last structure.

  2. Is there an easy way to retrieve the structures obtained from the scan as separate input files (e.g. .xyz or .gjf)?

I can use Gaussian 16 and Gaussview 5 or Gaussview 6.

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    $\begingroup$ This is question probably better suited at Matter Modeling. I'm almost confident it would be on topic there. Please don't repost the question there, instead we can migrate the question. Please leave a custom flag. $\endgroup$ Nov 18, 2023 at 13:10
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    $\begingroup$ I'm not too sure how NBO does behave for non-converged structures, it is probably dependent on what values you look at. Population analysis should still be quite okay. | Instead of using the modred interface, you might want to look at GIC, it is the superior interface! There might be the possibility to access different structures from a checkpoint file, and you could simply run a pop analysis over it in a second job. Any well-behaved molecular viewer (probably not Gausview) should be able to extract the steps of your scan in xyz coordinates. Have a look at Chemcraft or Avogardro. $\endgroup$ Nov 18, 2023 at 13:18
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    $\begingroup$ Look at this: chemistry.stackexchange.com/q/86646/4945 Try pop(always,nbo6). Never ever use the built in nbo module of Gaussian. This is incredibly old, has no support and plenty of know issues. This is only ever suitable for reproduction of values and showing that they are wrong. Also, part 2 of the question: chemistry.stackexchange.com/q/62530/4945 $\endgroup$ Nov 18, 2023 at 13:28
  • $\begingroup$ You may find helpful the book F. Weinhold and C. R. Landis, Valency and bonding : a natural bond orbital donor-acceptor perspective, Cambridge University Press (2005). $\endgroup$
    – PAEP
    Nov 18, 2023 at 18:16


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